It is well known to provide a pressure reducing and regulating valve which is manually or power operated to move a seal container between an inlet, an outlet and vent ports in response to fluid pressure.
However, it is desirable to minimize the size of the valve as this reduces its weight and cost. And more importantly, since a valve is a pressure vessel and the internal area of the valve is subjected to pressure, it is particularly desirable to minimize the size of the seal container which determines the size of the body and thus the magnitude of the internal expanding forces on the valve body. This becomes particularly important if the valve is to be face mounted such as subplate or manifold mounting. Conventionally, the primary and vent seals are positioned on the center line or central axis of the seal container. However, such axial placement of the seals require that the flow plate size accomodate the sum of the seal diameters and the stroke.
The present invention minimizes the size of the seal container by positioning the primary and vent seals on opposite sides of the central axis of the container, which allows the container and thus the valve to be of a smaller size, thereby reducing the pressure forces applied against the interior of the body. However, this non-axial placement of the seals creates force moments about the central axis due to the off-center drag of the seals and creates side loading on the container. The present invention reduces the side loading forces acting about the central axis by offsetting the primary and vent seals at distances from the central axis to compensate for the force moments.
Another problem in regulating and reducing valves is that the actuating means generally includes an adjustable screw engaging spring means acting against the seal container for adjusting the fluid flow through the valve. The screw includes a shoulder which is positioned to engage the body at each end of travel of the screw in opposite directions. If the adjusting screw overruns its limit of travel in each direction it binds on the body and is difficult to retract. The present invention is directed to utilizing one or more metal washers on each side of the shoulder coated with a low friction material whereby the shoulder can be easily backed off from its engagement with the body.